Backflow prevention devices are widely used to prevent undesirable flow reversal under low flow, static or backpressure situations wherein clean upstream fluid sources can be contaminated by downstream fluid. Backflow prevention devices typically comprise one or two check valves, housed within a valve body, which undergo closure under backflow, backpressure or back siphonage conditions. The use of backflow prevention devices is generally required by law for cross-connected water supplies where potable water could undergo contamination due to flow reversal or back pressure conditions.
Currently used double check valve backflow preventers have proved deficient in various respects. Particularly, such backflow preventers are prone to relatively high flow losses due to the valve configurations and closure mechanisms employed, especially under low flow conditions. In particular, the motion of the check valves either causes wear over time. Poppet valves have significantly less wear. However, they interrupt the flow to a higher degree.
Further, backflow preventer assemblies typically require a bulky, heavy cast housing with a side port tube or extension and a separately cast port cover. This type of housing is expensive to manufacture and requires a substantial amount of space to accommodate the side port tube and cover. Additionally, the cover typically undergoes a high amount of pressure requiring a thicker cover with more attachment points, which makes maintenance move inconvenient and difficult.
In addition, backflow preventer assemblies typically require pressure measuring ports. These ports allow measurement of pressure in each region of the backflow preventer to ensure proper operation. However, these ports require space between components of the backflow preventer assembly. This results in a longer backflow preventer assembly and, therefore, more cost in manufacture and installation. Particularly, the installation requires more space which increases the cost.
Moreover, reducing the length results in eddies within the current which can reduce the accuracy of pressure measurements. Since accuracy is essential to ensure proper operation, the typical response has been to simply refuse to shorten the length of the backflow preventer assembly. This contravenes the desire to reduce the flow length of the backflow preventer assembly, as described above.
Additionally, the increased length and material required in manufacture increases the weight of the backflow preventer assembly. This increases the difficulty in installing the backflow preventer assembly. Typically multiple people or an ad hoc support device are required simply to hold the assembly in the required position during assembly. This increases the installation time and cost.
Accordingly, there is a need in the art for a backflow preventer assembly which is compact and light weight. Further, there is a need in the art for a backflow preventer assembly which allows for accurate pressure measurement in each region, despite its compact nature. Moreover, there is a need in the art for a backflow preventer assembly which is easy and inexpensive to manufacture. Additionally, there is a need in the art for a backflow preventer assembly which provides easy access to internal check valves. Likewise, there is a need in the art for a backflow preventer assembly which has check valves with simple low-friction closure mechanisms. Furthermore, there is a need in the art for a backflow preventer assembly which provides low flow losses.